Substrates for magnetic discs, magnetic discs and process for producing magnetic discs

Abstract

A magnetic disc substrate is provided, which includes a magnetic disc substrate body made of glass and is characterized in that a metal element capable of absorbing light in at least a surface portion of the magnetic disc substrate body, and a texture is formed on a surface of the magnetic disc substrate body. Ions of the metal element are dispersed in the surface portion of the magnetic disc substrate, or the metal element is contained in a composition of the glass constituting the magnetic disc substrate in the form of an oxide. The glass is preferably a crystallized glass a Li 2 O--Al 2 O 3 --SiO 2 based crystallized glass, which particularly preferably contains 65 to 85 wt % of SiO 2 , 8 to 15 wt % of Li 2 O, 2 to 8 wt % of Al 2 O 3 , 1 to 5 wt % of P 2 O 5 and 1 to 10 wt % of ZrO 2 and has lithium disilicate (Li 2 O.2SiO 2 ) as a main crystalline phase.

What is claimed is: 
     
       1. A process for producing a magnetic disc substrate, comprising the steps of: polishing a surface of a glass magnetic disc substrate;   immersing the magnetic disc substrate into a melted salt of metal ions to incorporate a metallic element into at least the polished surface portion of the magnetic disc substrate, wherein said metallic element is capable of absorbing light having a wavelength of 1600 nm or less; and   irradiating high energy having a wavelength of 1600 nm or less upon the polished surface of the magnetic disc substrate, whereby said metallic element allows formation of a textured area on the surface of said magnetic disc substrate.   
     
     
       2. The process for producing the magnetic disc substrate set forth in claim 1, wherein the magnetic disc substrate comprises a reading/writing zone for recording the reproducing signals and a landing zone with which a magnetic head slider, the textured area having protuberances at heights of 50 to 200 Å is formed by irradiating the high energy light having a wavelength of 1600 nm or less upon the landing zone after finely polishing the surface of the magnetic disc substrate such that an area of top portions of said protuberances amounts to 2 to 5% of a total area of the landing zone. 
     
     
       3. The process for producing the magnetic disc substrate set forth in claims 1, wherein a laser beam selected from the group consisting of a YAG laser beam and an argon laser beam is used as said high energy light having a wavelength of 1600 nm or less. 
     
     
       4. The process for producing the magnetic disc substrate set forth in claims 1, wherein each of the protuberances constituting said textured area has an arched planar shape extending in a circumferential direction.